1. Field of the Invention
The present invention relates to an idle rotation speed learning control method and apparatus of an electronically controlled throttle type internal combustion engine. More particularly, the present invention relates to a method and apparatus for learning and correcting a target opening of a throttle valve at the time of idling, in an internal combustion engine having an electronically controlled throttle system for electronically controlling the opening of the throttle valve.
2. Description of the Related Art
Heretofore, there is known an electronically controlled throttle system where the throttle valve is opened and closed by an actuator such as a motor or the like, and a target air quantity is set based on an accelerator operation amount, and the opening of the throttle valve is electronically controlled to an opening giving the target air quantity.
Moreover, there is known a construction where, at the time of idling the engine, while feedback controlling the intake air quantity of the engine so that the engine rotation speed approaches a target idle rotation speed, when predetermined learning conditions materialized, the air quantity due to the feedback correction is learned as a fluctuation amount of a required intake air quantity due to friction of the engine or variations in the combustion efficiency, and a change amount in an opening area with lapse of time due to soiling or blocking of an intake system or deterioration or replacement of other parts, or the like. The intake air quantity and the target opening of the throttle valve are then corrected based on the learned values.
With the system as described above however, which collectively learns the fluctuation amount of the required intake air quantity and the change amount in the opening area only by the feedback control of the engine rotation speed at the idling time, the learning accuracy cannot be increased sufficiently. That is to say, with the above method, a discrepancy between a detection value of the throttle valve opening and the actual opening cannot be learned, and only the discrepancy of the detection value of the throttle valve opening with respect to the fluctuation amount of the required intake air quantity and the change amount in the opening area can be learned. Hence, the target opening of the throttle valve cannot be corrected sufficiently accurately in response to a required engine output.
The present invention addresses the above problems with the object of effecting control in an internal combustion engine comprising an electronically controlled throttle system, which makes the opening of the throttle valve correspond very accurately to the required engine output.
Moreover, it is another object of the present invention to effect control which makes the opening of the throttle valve correspond very accurately to the required engine output over a long period of time.
It is a further object of the present invention to be able to avoid the influence of programming bugs.